But the coldest of all is Minnesota at minus 55. That's colder than Mars. Yes, we mean the planet Mars.

Sunday's NFL playoff game in Green Bay, Wisconsin was one of the coldest in history. It was negative 5 with a windchill of negative 10.

The players strapped handwarmers to their waists and, on the sidelines, wore insulated capes and huddled around industrial heating fans. It was so cold, sportscaster Erin Andrews cut short her post-game interview.

People are posting their cold weather experiments on YouTube. One person threw a pot of boiling water into the air and it instantly turned to steam.

Also on YouTube, someone found that a bottle of water left in a car overnight turns to ice when you shake it.

Another person showed that when you blow a bubble at minus 15 degrees, it freezes.

But here's something you definitely shouldn't try. One goofball in Minnesota is dared by his friends to lick a frozen pole. You know what happens next. His friends are laughing but it's actually very dangerous. A cup of hot water did the trick and he broke free. But he may have permanently damaged the taste buds on his tongue.

So, if the polar vortex is heading your way, the best advice is to stay inside and bundle up.